Electrically heated die-cutting apparatus

ABSTRACT

A DIE-CUTTING APPARATUS HAVING A DIE BLADE CONNECTED INTO AN ELECTRICAL CIRCUIT AND ADAPTED TO HAVE THE THE BLADE ELECTRICALLY RESISTIVELY HEATED BY THE METHOD OF PASSING AN ALTERNATING CURRENT THERETHROUGH AND A METHOD FOR USING ELECTRICALLY RESISTIVELY HEATED DIE BLADES FOR DIE-CUTTING A GRAPHIC PATTERN FROM A THIN CUTTABLE MATERIAL LAYER IS SHOWN. IN ONE EMBODIMENT OF A DIE-CUTTING APPARATUS, A PLURALITY OF DIE BLADE SEGMENTS IS FORMED INTO A GRAPHIC PATTERN, IS ELECTRICALLY CONNECTED IN AN ELECTRICALLY CONDUCTIVE NETWORK AND IS RESISTIVELY HEATED BY PASSING AN ALTERNATING CURRENT THERETHROUGH. THE APPARATUS IS ADAPTABLE TO BOTH KISS CUTTING AND THROUGH CUTTING. THE ELECTRICALLY HEATED DIE BLADE MAY BE SUBSTANTIALLY ENCLOSED IN A HEAT-INSULATING FOAMY LAYER TO RETARD HEAT DISSIPATION.

United States Patent [72] Inventors AlbertlfiennetllOlson 415x 279 111III 333 8800 no North Oak; Raymond C. Ludel, White Bear Lake, Min.

[21] Appl. No. 750,242

Assistant Examiner-Leon Gilden Attorney-Kinney, Alexander, Sell, Steldt& Delahunt [22] Filed Aug. 5, 1968 [45] Patented June 28, 1971 [73]Assignee Minnesota Mining and Manufacturing Company Saint Paul,Minnesota [54] ELECTRICALLY HEATED DIE CU'I'TING APPARATUS ABSTRACT: Adie-cutting apparatus having a die blade con- 2 Claims, 13 Drawing Figs.

nected into an electrical circuit and adapted to have the die bladeelectrically resistively heated by the method of passing an alternatingcurrent therethrough and a method for using electrically resistivelyheated die blades for die-cutting a graphic pattern from a thin cuttablematerial layer is shown. in one embodiment of a die-cutting apparatus, aplurality of die blade segments is formed into a graphic pattern, iselectrically connected in an electrically conductive network and isresistively heated by passing an alternating current [56] ReferencesCited UNITED STATES PATENTS 1,082,985 12/1913Wilder..........................

1,411,774 4/1922 Engel.... 1,449,445 3/1923 PATENTEU JUN28I97I 3587-377.

VOLTAGE Sou/QC:

N E 0R$ ALBERT KENNETH OL5QN Rfi YMQND C. LUNDELL ATTORNEYS PATENTEUJUN28 1971 SHEET 2 UF 3 FIG. 4

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1N VE TOAKS A1. 5597' KENNETH 0L SON RA YMOND C1 LUNDELL.

BY 6 I M M f NM ATTORNEYS sum 3 or 3 FIG. 7c a HIGH PEOUENCY VOLTAGE50mm Q I/vvE/v TORS ALBERT KENNETH OLSON RABKXMO'ND Cf LUNDELL 6 91 .04Wand? A 7- TOANE Y5 ELECTRICALLY HEATED DIE-CUTTING APPARATUS Hot andcold die-cutting of graphic patterns from sheeting and film is known.For example, graphic patterns may be kiss cut from pressure-sensitiveadhesive coated materials such as 3M Scotchlite" brand reflectivesheeting, 3M "Scotchcal brand vinyl film and the like using knownkiss-cutting apparatus having a plurality of die blades.

By using a heated die blade, a cleaner more uniform cut is obtained thanwith an unheated blade since the heat operates on these materials incombination with the blade to part the material more evenly. Also, whenhot die-cutting reflective sheeting, such as 3M "Scotchlite brand, theheat provided operates upon the cut edges of the sheeting to seal thesecut edges from corrosion.

Prior-art methods of heating die blades of die-cutting apparatushave-included conduction heating techniques. in one well-known prior-artmethod, the die blades were formed into graphic patterns and were heatedby direct contact from a source of heat by placing the noncutting edgeof the die blade into physical contact with a heated platen. After thecutting edge of the die blades was conductively heated to a desiredtemperature, the die-cutting apparatus was used for kiss cutting agraphic pattern from a thin cuttable material layer.

There are several attendant disadvantages to the known prior-art methodof conductively heating die blades. For example, limitations are imposedas to both the type of die press which can be used with such diecuttingapparatus and the maximum practical size of the graphic pattern ordesign which can be formed by the die-cutting apparatus die blades andbe die-cut from the thin cuttable material layer using such a die press.

This known prior-art conduction heating method also has inherentoperational shortcomings. in some instances, up to approximately Hihours may be required to heat the plurality of die blades to the desiredtemperature. in the prior-art conduction heating method, the heatingtime depends on the size and material of the die blades and on theheating energy supplied by the platen heat source.

Another important shortcoming of the prior-art conduction heating methodincludes that the noncutting edge of the die blade, which edge contactsthe heated platen, must be heated to a higher temperature than thatrequired at the cutting edge in order to compensate for heat loss orheat drop through the blade so as to obtain the predeterminedtemperature at the cutting edge of the die blades. Also, heat from theheating platen must be supplied, at the higher temperature, at a heatingrate substantially equal to the heat loss from both the heat drop acrossthe die blade and the heat loss from the apparatus during thedie-cutting operation.

The prior-art method of conductively heating die blades is limited touse with platen die presses and cannot practically be used with areciprocating die press of the type wherein the die and cuttablematerial layer being die-cut are simultaneously fed through the press.

Another disadvantage of the prior-art method and apparatus is that theyare not adaptable for use with existing diecutting equipment fordie-cutting large intricate patterns and designs used by the automotiveindustry for decorative striping on automobiles.

it is therefore one object of this invention to provide a noveldie-cutting apparatus having a die blade which is capable of beingelectrically resistively heated.

it is another object of this invention to provide a die-cuttingapparatus having a die blade which is capable of being electricallyresistively heated and which is capable of being unrestricted in itsgraphic pattern configuration in at least one dimension compared to thedimensions of the die press with which it is to be used.

It is another object of the present invention to provide apparatus fordie-cutting graphic patterns from thin cuttable material layers whereinthe die blade has a relatively short heating time which results in moreproductive time than the prior-art methods and apparatus.

Briefly, the invention comprises a die-cutting apparatus having a dieblade which is electrically connected into an electrically conductivepath and which is electrically resistively heated by passing anelectrical current through the electrically connected die blade.

in the preferred embodiment, the die blade is formed of material capableof being electrically resistively heated to a predetermined temperatureby passing an electric current therethrough and is capable when soheated of cutting a graphic pattern from a thin'cuttable material layer.The blade is shaped into the graphic pattern and also is formed into anelectrically conductive path for the current flow. Circuit means adaptedto be electrically connected to a variable voltage source areelectrically connected directly to the die blade to enable current flowthrough the die blade to heat the same when the circuit means areconnected to the voltage source. When cutting a cuttable material layer,the power supply is at first varied to observe the cutting effect of theheated die blade at different levels of supplied current in order todetermine what range of supplied current the power supply for thecircuit should be operated to provide quality cutting. A thermocoupleplaced near the cutting edge of the die blade allows determination ofthe temperature range in which quality kiss cutting of a selected thincuttable material layer can be achieved.

The above-noted advantages of the invention will become readily apparentwhen considered in light of the following description of a preferredembodiment, which refers to the accompanying drawing wherein:

FIG. 1 is an isometric view illustrating a die-cutting apparatus havinga die blade made of a plurality of die blade segments constructed inaccordance with the teachings of the present invention;

MG. 2 is an isometric view illustrating the die-cutting apparatus of HG.l with the die blade cutting edges enclosed in a heat insulating foamymaterial to retard heat dissipation;

FlG. 3 is a top view of FIG. 2 illustrating the die blade edges enclosedin the heat-insulating foamy material layer;

HO. 4 is a bottom view of FIG. 1 illustrating the noncutting edges ofthe die blade, which die blade is rigidly supported in a rigid support;

FIG. 5 is a front sectional side view partially in cross section takenalong section line 55 of F lG. 3;

FIG. 6A is a schematic diagram partially in block and pictorial formillustrating one embodiment of the present invention wherein theplurality of die blade segments is connected into a series electricalnetwork energized from a voltage source;

H6. 68 is a schematic diagram illustrating an equivalent electricalcircuit and energizing voltage source for the embodiment of HG. 6A;

FIG. 7A is a partial view illustrating another embodiment of the presentinvention wherein the plurality of die blade segments is connected intoa series-parallel electrical network;

FIG. 7B is a schematic diagram illustrating an equivalent electricalcircuit of the embodiment of PEG. 7A and also showing a voltage sourceused in association therewith;

FIG. 7C is a schematic diagram illustrating an equivalent circuit of amodification of the equivalent circuit of FIG. 7B;

FlG. 8 is a partial pictorial representation illustrating a top view ofan alternate embodiment of a die-cutting apparatus wherein the dieblades are formed in a continuous strip;

FIG. 9 is a pictorial and block representation illustrating yet anotherembodiment of a die-cutting apparatus wherein the die blade is formedinto a cylinder having a thin wall and which is capable of beingelectrically resistively heated using induction heating by a highfrequency voltage source; and

FIG. 10 is a pictorial representation illustrating a reciprocating diepress which is capable of carrying out the kiss-cutting method with adie-cutting apparatus of the present invention.

FlG. ll illustrates a perspective view of the die-cutting apparatus ofthe present invention. Typically, known die-cutting apparatus utilize aplurality of die blade segments wherein each die blade segment is shapedinto a predetennined form in relation to the others to form a desiredgraphic pattern. For example, in FIG. 1, the die blade segments 10 areshaped to form two portions 10 and 12 defining a graphic pattern of twoconcentric loop patterns 12 and 14. Preferably, the die blade segments10 are constructed from flexible steel rule. While steel rule isflexible, there are limitations in the graphic patterns into which apiece of steel rule can be shaped. Thus, as illustrated in FIG. I, it issometimes necessary to use a plurality of die blade segments 10. Gaps 15are shown between the die blade segments 10. The illustrated size of thegaps 15 is greatly exaggerated for the purpose of showing theirexistence. Ideally, the die blade segments 10 would be physicallypositioned in contiguous relationship to each other thereby providing asubstantially continuous cutting edge.

In the preferred embodiment of the present invention, at least onespatial discontinuity or gap is provided in each loop. Thesediscontinuities provide an electrically nonconductive gap in the dieblade. An electrically nonconductive thermal conductor 17, such as aceramic material, can be inserted into this gap in order to provide acontinuous cutting edge. If desired, each concentric loop configuration12 and 14, illustrated in FIG. 1, could be made as one continuoussegment having only a single electrically nonconductive gap as describedabove.

The die blade segments 10 forming loops 12 and 14 are mounted in amounting means such as rigid support 16 in order to prevent flexing ofthe die blade segments 10. The rigid support 16 may be formed of anonconducting insulating material, such as, for example, wood,preferably plywood or hardboard. The mounting means or rigid support 16has an aperture therethrough for receiving the noncutting edge of thedie blade segment which rigidly supports the die blade in a positionenabling the die blade to extend from one side of the rigid support 16.The die blade segments 10 have notches 18 (illustrated in FIGS. 4 and 5)to improve the gripping relationship between the die blade segments 10and the rigid support 16.

It is preferable to enclose the cutting edge 19 of the die blade 10 in aresilient heat insulating foamy material layer 20 (illustrated in FIGS.2, 3 and 5). A foamy silicone rubber may be used as the heat-insulatingfoamy material layer 20.

In FIGS. 2 and 5, the heat-insulating foamy material layer 20, in itsrelaxed state, extends slightly beyond the cutting edge 19 of bladesegments 10. When the foamy material layer 20 is compressed, the cuttingedges of the die blade segments extend through the foamy material layer20.

The foamy material layer 20 retards heat dissipation from the die bladesegments 10, thereby decreasing the amount of heat which must besupplied to the blades. Being extended beyond the cutting edge 19 of thedie blade, the insulating material layer 20 also serves to hold theheated cutting edge 19 of the die blade away from the thin cuttablematerial layer both before and after a graphic pattern is cut therefrom.The insulating foamy material layer 20 defines passageways 22 and 24through which the cutting edges of the die blade segments pass whencutting a graphic pattern from a thin cuttable material layer.

FIG. 3 illustrates a top view of the die-cutting apparatus of FIG. 2. InFIG. 3, the inner and outer die blade loops 12 and 14 are shown to beenclosed by the heat-insulating foamy material layer 20 and to besituated in passageways 22 and 24. In this embodiment, the dimension ofthe insulating foamy material layer 20 in its relaxed state is less thanthe dimension of the rigid support 16 but greater than the dimensions ofthe die blade loops 12 and 14.

FIG. 4 illustrates a bottom view of the die-cutting apparatus of FIG. 1.In FIG. 4, the noncutting edges 21 of each die blade segment extendthrough the apertures in rigid support 16 and are thereby securelymounted to the rigid support 16.

FIG. 5, which is a section taken along lines 5-5 in FIG. 3, illustratesthis mounting in detail. The die blade segment 10 has notches 18 on itsnoncutting edge 21 which die blade segment 10 is located in the rigidsupport 16. Also, the relationship between the insulating material 20 inthe relaxed position and the die-cutting edges of die blade segment 10is illustrated. The degree of the extension of the insulating materiallayer 20 beyond the cutting edge 19 is exaggerated in FIG. 5 forpurposes of showing its existence. The noncutting edge 21 of the dieblades is preferably constructed flush with the outer surface 23 ofrigid support 16.

Based on the teachings of this invention, the die blade segments 10 canbe directly heated by electrically connecting them as a resistance loadin predetermined electrical circuit configurations and applying avoltage across the electrical circuit to cause an electrical current topass through the die blade segments 10. Referring again to FIG. 1, thedie blade segments 10 are soldered together, such as shown by junctions26 at certain of the gaps 15, to give electrically conductive integrityto the cutting blade. For example, silver solder can be used forelectrically connecting the die blade segments 10 because silver solderhas ahigher melting temperature than the temperature to which the dieblade segments 10 are heated. Alternatively, the die blade segments 10can be mechanically joined together, such as by nuts and bolts, to formthe desired electrical circuit.

In the embodiment of FIG. 1, the die blade segments 10 are electricallyconnected in series such that a uniform current can pass through eachdie blade segment. Connections between the inner die blade loop 14 andthe outer die blade loop 12 are made by silver soldering a suitablesized copper wire connection 28 between the ends of an inner loop dieblade segment and an outer loop die blade segment. The wire is largeenough so as not to appreciably heat up when current flows through thedie blade segments 10. Circuit mean s operatively connected to the dieblade segments 10, such as power leads 30 and 32, are adapted to have avoltage applied thereacross to pass a current through the electricalcircuit formed of the die blade segments 10 for resistively heating thedie blades to a predetermined temperature.

In the embodiment of FIG. 1, an electrically conductive path is formedthrough lead 30 to die blade segment 34, then through the remaining dieblade segments which form the inner die blade loop 14 to wire 28 andthen through the die blade segments which form outer die blade loop 12to die blade segment 36 which is connected to power lead 32. In thisembodiment, electrically nonconductive gaps 38 and 40 are maintained inthe outer and inner loops 12 and 14 respectively so that all die bladesegments 10 are connected in series. The series connection results inthe same current flowing in all segments and is generally preferred.

After the electrical connections are completed, the blades are coveredwith an insulating foamy material layer 20 as illustrated in FIGS. 2, 3and 5. The passageways 22 and 24 are formed in insulating foamy materiallayer 20 by placing the uncut insulating foamy material layer on top ofthe cutting edges 19 and then making an initial pass through the press,thereby cutting the insulating material layer 20 with the blade loops 12and 14.

FIG. 6A is a schematic diagram illustrating the die blade segments 10 aspart of an electrical circuit. In FIG. 6A, an electrical circuit isformed by connecting the die blade segments together into a network 42and applying a voltage from a voltage source 44 across the network 42.In the preferred embodiment, the voltage source 44 is a variablealternating current voltage source. A voltmeter 46 and an ammeter 48 maybe utilized with the circuit to measure the electrical power beingsupplied to the die blade network 42. In this manner, the magnitude ofthe current can be regulated to maintain a relatively constantpredetermined temperature in the die blade network 42.

FIG. 6B is a schematic diagram illustrating the equivalent circuit ofFIG. 6A wherein the die blade network 42 is represented as a resistor 50placed across a variable transformer 52 connected to an AC voltagesource 54. A thermocouple 56 can also be physically mounted onto the dieblade near the cutting edge 19 to measure the temperature for purposesof maintaining the cutting edges H9 at a predetermined temperature usingcurrent regulation as discussed with respect to FlG. 6A.

In theembodiment described in relation to FIGS. l-6B, theseries-connected die blade segments 10 are formed into a graphic patterncomprising two concentric loops 12 and 14. For purpose of example, acutting apparatus so constructed can be used for kiss-cutting graphicpatterns from a thin cuttable material such as a pressuresensitiveadhesive coated vinyl film having a thickness of about 0.003 inch toabout 0.005 inch (about 76.2 1. to about 127p.) and having apressure-sensitive adhesive coated thereon. Such a thin cuttable layeris described in US. Pat. No. 2,647,848. The pressure-sensitive adhesivecoated vinyl film is mounted in releasable engagement with a paperbacking having a thickness of about 0.004 inch to about 0.006 inch(about 101.6 to about l52.4p.) which backing has been impregnated with apolyethylene and silicone impregnator.

The die blade segments 10 are electrically resistively heated by aconnection to an alternating current voltage source to a predeterminedtemperature of about 200 F. (about 93 C.). In the kiss-cutting method,the dwell time of the cutting edge on the pressure-sensitive adhesivecoated film mounted on an impregnated paper backing in order to kiss cuta graphic pat tern from the vinyl film and adhesive is in the order ofonetenth of a second.

it is contemplated that a person skilled in the art could determine theproper predetermined temperature, dwell time and the like for the typeof cuttable'material layer in order to obtain clean, smooth cuts. It isalso contemplated that a person skilled in the art could determine thevoltage and current ratings for the voltage source upon knowing the sizeand resistance of the die blade. If desired, multiple layers of cuttablematerial could be through cut by the die-cutting apparatus and methoddisclosed herein. Generally, it has been determined that forkiss-cutting materials such as 3M Scotchcal" brand vinyl film type 3650,it was required to heat the cutting edges of the die blades to about 200F. to about 220 F. (about 93 C. to 105 C.).

ln the embodiment of the invention described above, the die bladesegments 10 were adapted to be connected as a series resistance element.A series connection is but one embodiment. ln certain cuttingconfigurations, such as that shown in FIG. 7A, the proximity of thevarious die blade segments 58 and 60 to each other may give rise to ahigher temperature at their cutting edges than in those die bladesegments 62 which are not as close to other die blade segments becauseof greater heat transference between the closer segments 5% and 60. Insuch a configuration, it may be desirable to pass a different magnitudecurrent through the die blade segments 58 and 60 than through die bladesegments 62 to compensate for the relatively higher heating of the dieblade segments 58 and 60 due to their relative proximity, in order toprovide a more uniform temperature all along die blade segments 58, 60and 62.

To achieve compensation, the die blade segments 58 are connected inseries at junctions 64 and connected in parallel by wires 66 and 68 withsegments 60 which segments 60 are connected in series at junctions 70.This parallel combination is connected in series with the segments 62 atjunction terminals 72 and 74. The higher current thus flows throughsegments 62.

This combination is represented in the schematic diagram of FIG. 7Bwhich is an equivalent circuit of HG. 7A wherein die blade segments 58,60 and 62 are represented by resistors 76, 78 and 80 respectively.

Referring to H6. 7C, variable resistor elements 82, 84 and 86 areconnected in series with the die blade segments 58, 60 and 62 of FIG. 7Awhich are represented by resistors 76, 73 and 80 in FIGS. 7B and 7C andthus provide the capability of achieving more precise regulation of thecurrent in each branch of die blade segments.

FIG. 8 illustrates another embodiment wherein separate voltage suppliesmay be used to supply currents to separate continuous die blades inorder to provide a more uniform temperature to the die blade cuttingedges. Current through die blade 88 may be supplied by a second voltagesource at terminals 90 and 92 while current through die blade 94 issupplied by a second voltage source at terminals 96 and 98. The voltageare varied to cause the desired magnitude of current to flow in both dieblades 88 and 94.

An alternative method of heating a die blade by establishing an eddycurrent through an endless continuous die blade is by transformer orelectrical induction action. The die blade is disposed in a magneticfield established by an induction coil such that the die blade functionsas a shorted secondary winding. An eddy current is established whichelectrically resistively heats the die blade to the predeterminedtemperature.

FIG. 9 illustrates a preferred embodiment wherein a cylindrical dieblade 100 is mounted coaxially with a cylindrical coil 102. Preferably,the transformer heating method should utilize a choice of frequencywhich is appropriate for the size of the die blade being heated.

From the foregoing, it should be appreciated that a die blade adapted tobe electrically resistively heated by passing a current through the dieblade and the novel method of so heat ing a die blade have beendisclosed herein. It is readily apparent to one skilled in the art thatthe disclosed invention presents several advantages not found inprior-art apparatus and methods. For example, the apparatus of thepresent invention can be used with more than one type of die press. Itcan be readily used with the reciprocating die press 104 as illustratedin FIG. 10. One such die press which may be used for practicing thisinvention is a Hytronic Series 60 cutting press manufacture by UnitedShoe Machinery Corporation.

in H6. 10, a die-cutting apparatus 106 having an elongated piece ofmultilayer material 108 containing a thin cuttable material layer H09which is to have a graphic pattern kiss cut therefrom is in contactingengagement with the insulating material layer 20 portion of thedie-cutting apparatus 106 with the thin cuttable material layer 109contacting the insulating material layer 20. The assembled die-cuttingapparatus 06 and multilayer material 108 in combination is passedthrough the die press 104- from left to right. As the assembly isadvanced incrementally through the press die, a graphic patterncorresponding to the graphic pattern formed by the die blade cuttingedges is kiss cut from the thin cuttable material layer H09 asillustrated by dashed lines 110.

An electrically insulating material member 112 separate from thedie-cutting apparatus is situated between the press bed 114 and themounted die-cutting apparatus 106. This electrically insulating materialmember 112 may be rigidly affixed to the noncutting side of the mounteddie-cutting apparatus 106 or onto the press bed 114.. A preferredinsulating material is bakelite sheeting.

The present invention allows the die blade to be portable and a heatingsystem need not be contained within the die press. Also, the apparatusof the present invention gives rise to more flexibility in die designchange since the dimensions of the design are not wholly restricted tothe dimensions of the die press and heat transmission medium, such asthe heated platen of the prior-art apparatus. Furthermore, with theapparatus of the present invention, the die blade can be heated in amatter of only a few minutes instead of up to approximately 1% hoursthus resulting in a considerable reduction in both nonproductive heatdissipation and in nonproduetion time. Also, the fact that only the dieblade is being heated, instead of both the die blade and an auxiliaryheat transmission medium, results in further reduction of nonproductiveheat dissipation.

Electricaily resistively heated cutting die blades have wide utility. inone application, the novel die-cutting apparatus was used incontrolleci-depth cutting or kiss-cutting letters or designs in vinylfilm.

An example of this utility is for kiss-cutting pressure sensitiveadhesive coated vinyl film, such as that sold under the trade name ofScotchcal brand No. 3650, in predesigned configurations. Consider theprespaced design stripes which are applied to automobiles. These stripesare a pressure-sensitive adhesive coated film having a paper backing.Higher quality cuts, that is cleaner cuts, of the pressure-sensitiveadhesive coated vinyl film are obtained when the cutting die is heatedto a predetermined temperature. The design is cut through the materialbut not through the paper backing by the kiss-cutting technique usingelectrically respectively heated die blades. After the cut is made, thematerial not essential to the design is stripped from the backing anddiscarded.

A 7-foot (about 2.1 m.) decal adapted for use as a racing stripe waskiss cut from a pressure-sensitive adhesive coated vinyl film generallyknown as 3M "Scotchcal" brand film type No. 3650. The vinyl film was ofapproximately 0.004 inch (about 10011.) in thickness and was releasablysupported on a backing member formed of a silicone-impregnated paperbacking of approximately 0.006 inch (about 150p.) thickness. Thepressure-sensitive adhesive used to coat the vinyl film is selected tohave a peel-back characteristic which permits the vinyl film to bepeeled from the paper backing with the pressure-sensitive adhesiveretained on the peeled away vinyl film. The decal or design formed ofthe vinyl film can thus be permanently positioned on the exterior of anautomobile.

The above-described decal was kiss cut using a die blade which wasapproximately 7 feet (about 2.1 m.) in length, approximately 1 inch(about 2.5 cm.) high and approximately 0.030 inch (about 760p.) thick.The die blade segments of the 7-foot (about 2.1 m.) die-cuttingapparatus were silver soldered together in a series electrical network,the equivalent of which is illustrated in FIG. 6B. The die blade wasconnected to an AC power supply capable of delivering more than 100amperes at 60 Hz. at approximately 30 volts. An ammeter and voltmeterwere used to measure the current and voltage being supplied to theblade. A thermocouple was impressed near the cutting edge of the dieblade.

At a current of approximately 30 amperes, and a measured temperature inthe order of 200 F. to 220 F. (about 93 C. to 105 C.), the cleanest,most uniformly cut graphic patterns were obtained. Thus, thepredetermined temperature for this combination of die blade and cuttablematerial is in the order of 200 F. to 220 F. (about 93 C. to 105 C.).The die blade temperature could be varied by varying the input voltagewhich in effect varied the current. The kiss-cutting die blades wereheated to this predetermined temperature in approximately 2 to 3minutes.

Once the current giving rise to the predetermined temperature for agiven combination of apparatus and cuttable material is known, thecircuit may be preset for a given current magnitude and temperature neednot be directly measured. The technique of presetting the currentmagnitude was effective to maintain the die blade temperature within afew degrees of the desired predetermined temperature.

The temperature at the notches was observed to be approximately F.(about 11 C.) higher. Heat dissipation from the 7-foot (about 2.1 m.)kiss-cutting die apparatus was reduced by enclosing the heatedkiss-cutting die blade with a heat-insulating foamy material layer asdescribed herein.

it is contemplated that a temperature sensor could be physically locatedon a die blade and be used in a feedback temperature control systemwhich varies the input current or voltage as required in order tomaintain the desired predetermined temperature. Such feedbacktemperature control system may be desired in the event the kiss-cuttingoperation is automated.

We claim:

1. A die-cutting apparatus for forming a graphic pattern from a thincuttable material layer, comprising a-die blade having a cutting edgeand being shaped into said graphic pattern, wherein the die blade isformed of material capable of being electrically resistively heated to apredetermined tempera when the die blade is heated to said predeterminedtemperature the die blade is capable of cutting said graphic patternfrom said thin cuttable material layer upon the cutting edge engagingsaid thin cuttable material layer, and wherein the die blade definingthe graphic pattern contains at least one die blade portion defining aclosed pattern, which die-cutting apparatus is characterized by theimprovement that the die blade forms an electrically conductive currentpath;

the die-cutting apparatus further comprises power leads electricallyconnected to the die blade for electrically connecting a voltage sourceof a predetermined voltage to the die blade to produce current flowthrough the die blade to uniformly heat the cutting edge of the dieblade to the predetermined temperature; and

said die blade portion defining a closed pattern includes at least onethermally conductive electrically nonconductive material segment in theblade to define an electrically nonconductive gap in the die blade, atwhich gap said die blade portion is operatively coupled to the powerleads.

2. A die-cutting apparatus for forming a graphic pattern from a thincuttable material layer, comprising a die blade having a cutting edgeand being shaped into said graphic pattern, wherein the die blade isformed of material capable of being electrically resistively heated to apredetermined temperature by passing an electric current therethroughand wherein when the die blade is heated to said predeten-ninedtemperature the die blade is capable of cutting said graphic patternfrom said thin cuttable material layer upon the cutting edge engagingsaid thin cuttable material layer, wherein the die blade includesportions positioned in a noncontiguous relationship to one another,which die-cutting apparatus is characterized by the improvement that thedie blade forms an electrically conductive current path;

the die-cutting apparatus further comprises power leads electricallyconnected to the die blade for electrically connecting a voltage sourceof a predetermined oltage to the die blade to produce current flowthrough the die blade to uniformly heat the cutting edge of the dieblade to the predetermined temperature; and

said noncontiguous portions are electrically connected in series circuitrelationship to one another, wherein each said noncontiguous portionprovides an open loop current path.

ure by passing an electric current therethrough, wherein

